U.S. Pat. No. 4,554,996 disclosed and claimed a rope ladder of the type in which there were two ropes on each side of an improved molded step, and in which a wedging structure secured the attachment between each step and the ropes. A strong, specially shaped, metal frame was provided, and around it was molded the body of the step.
However, some problems developed. Regardless of the amount of quality control exercised in the drilling of the bolt-receiving holes at each end, after the molding was completed, it seemed possible to obtain a perfect alignment of the holes, as was needed in order to secure the steps to the collars. Apparently, the flexibility of the molded elastomer caused the trouble. Attempts to solve this problem seemed to lead to structures that were too expensive for maintaining a competitive position.
Another problem was that when stainless steel bolts were used to avoid corrosion in salt water and when the step frame was made with a lightweight steel alloy, the two different metals were placed in contact. Then, in sea water, bimetallic corrosion resulted. This also happened with the horizontal bolts used in replacement steps like those shown in U.S. Pat. No. 4,554,996.
Also, the metal collars, were heavy, and when attempts were made to employ collars made of plastic materials, the ropes tended to slip, for suitably strong plastics tend to be slick and slippery.